Quick Question

[9homie]

Hello.

I need help with some things that i have said at the bottom of the code...

<?php
require_once('db.php');
include('functions.php');

if(isset($_POST['register']))
{
    if($_POST['username']!='' && $_POST['password']!='' && $_POST['password']==$_POST['password_confirmed'] && $_POST['email']!='' && valid_email($_POST['email'])==TRUE && checkUnique('Username', $_POST['username'])==TRUE && checkUnique('Email', $_POST['email'])==TRUE) 
    {

        $query = mysql_query("INSERT INTO users (`Username` , `Password`, `Email`, `Random_key`) VALUES ('".mysql_real_escape_string($_POST['username'])."', '".mysql_real_escape_string(md5($_POST['password']))."', '".mysql_real_escape_string($_POST['email'])."', '".random_string('alnum', 32)."')") or die(mysql_error());

        $getUser = mysql_query("SELECT ID, Username, Email, Random_key FROM users WHERE Username = '".mysql_real_escape_string($_POST['username'])."'") or die(mysql_error());

        if(mysql_num_rows($getUser)==1)
        {//there's only one MATRIX :PP

            $row = mysql_fetch_assoc($getUser);
            $headers =     'From: [e-mail]' . "\r\n" .
                        'Reply-To: [e-mail]' . "\r\n" .
                        'X-Mailer: PHP/' . phpversion();
            $subject = "Activation email from ourdomainhere.com";
            $message = "Dear ".$row['Username'].", this is your activation link to join our website. In order to confirm your membership please click on the following link: http://www.ourdomainhere.com/confirm.php?ID=".$row['ID']."&amp;key=".$row['Random_key']." Thank you for joining";
            if(mail($row['Email'], $subject, $message, $headers))
            {//we show the good guy only in one case and the bad one for the rest.
                $msg = 'Account created. Please login to the email you provided during registration and confirm your membership.';
            }
            else {
                $error = 'I created the account but failed sending the validation email out. Please inform my boss about this cancer of mine';
            }
        }
        else {
            $error = 'You just made possible the old guy (the impossible). Please inform my boss in order to give you the price for this.';
        }

    }
    else {        
        $error = 'There was an error in your data. Please make sure you filled in all the required data, you provided a valid email address and that the password fields match';    
    }
}
?>
<?php if(isset($error)){ echo $error;}?>
<?php if(isset($msg)){ echo $msg;} else {//if we have a mesage we don't need this form again.?>
<form action="<?=$_SERVER['PHP_SELF']?>" method="post">
    Username: <input type="text" id="username" name="username" size="32" value="<?php if(isset($_POST['username'])){echo $_POST['username'];}?>" /><br />
    Password: <input type="password" id="password" name="password" size="32" value="" /><br />
    Re-password: <input type="password" id="password_confirmed" name="password_confirmed" size="32" value="" /><br />
    Email: <input type="text" id="email" name="email" size="32" value="<?php if(isset($_POST['email'])){echo $_POST['email'];}?>" /><br />
    <input type="submit" name="register" value="register" /><br />
</form>
<? } ?>
require_once('db.php');
include('functions.php');

So what does the REQUIRE_ONCE('DB.PHP'); mean? What folder does it connect to and what does it do? Is it the Login or Registration.
The same question with INCLUDE('FUNCTIONS.PHP');

and do i need them?

Thanks in advance people.

[NogDog]

I believe most of your questions are answered in the [man]include[/man] page, then see the [man]require_once[/man] page for what is different for that specific command.